Molecular mechanisms of traumatic brain injury in children. A review

Early diffusion restriction of white matter in infants with small subdural hematomas is associated with delayed atrophy

BACKGROUND

Traumatic brain injury (TBI) is a major cause of infant morbidity and mortality. In these patients, magnetic resonance imaging (MRI) including diffusion-weighted imaging (DWI) is the test of choice to describe the extent of microstructural injury.

CASE PRESENTATION AND DISCUSSION

In this case series, we describe novel acute and chronic MRI findings in four infants (6-19 months) with small, unilateral subdural hematomas in whom the etiology of head injury was suspicious for non-accidental trauma (NAT). Acute (<1-week post-injury) DWI revealed extensive areas of restricted diffusion isolated to the cerebral white matter predominantly ipsilateral to the subdural hematoma. After prolonged pediatric intensive care treatment including subdural evacuation (n = 2) or decompressive craniectomy (n = 1), all patients survived albeit with significant motor and cognitive deficits. Delayed structural MRI (6-9-year post-injury) demonstrated cortical and subcortical atrophy well-correlated with areas of acute restricted diffusion.

CONCLUSION

These four cases highlight that relatively small subdural hematomas can be associated with extensive white matter injury-detectable only by early DWI-which have long-term structural and functional consequences.

Demographic and injury-related moderators of memory and achievement outcome in pediatric TBI

Critical factors affecting traumatic brain injury (TBI) outcome in children and adolescents are explored with an emphasis on an examination of age at injury as a predictor of memory functioning. Age at injury and other injury-related and demographic predictors (i.e., severity, time postinjury, gender, and socioeconomic status [SES]) of memory and achievement outcome were examined in 65 children and adolescents post-TBI compared to 65 age-matched noninjured controls. Although robust findings have been found for age at injury as a general predictor of outcome, age was not found to be a significant predictor of memory functioning following pediatric TBI. Structural equation modeling suggests that the most parsimonious model of post-TBI outcome contains two causally related latent variables: one defined by gender, SES, injury severity, and age at injury, and one defined by general cognitive functioning.

Translocator protein (18 kDa) TSPO: an emerging therapeutic target in neurotrauma

Traumatic brain injury (TBI) induces physical, cognitive, and psychosocial deficits that affect millions of patients. TBI activates numerous cellular mechanisms and molecular cascades that produce detrimental outcomes, including neuronal death and loss of function. The mitochondrion is one of the major targets of TBI, as seen by increased mitochondrial activity in activated and proliferating microglia (due to high energy requirements and/or calcium overload) as well as increased reactive oxygen species, changes in mitochondrial permeability transition, release of cytochrome c, caspase activation, reduced ATP levels, and cell death in neurons. Translocator protein (TSPO) is an 18-kDa outer mitochondrial membrane protein that interacts with the mitochondria permeability transition pore and binds with high affinity to cholesterol and various classes of drug ligands, including some benzodiazepines such as 4'-chlorodiazepam (Ro5-4864). Although TSPO levels in the brain are low, they are increased after brain injury and inflammation. This finding has led to the proposed use of TSPO expression as a marker of brain injury and repair. TSPO drug ligands have been shown to participate in the control of mitochondrial respiration and function, mitochondrial steroid and neurosteroid formation, as well as apoptosis. This review and commentary will outline our current knowledge of the benefits of targeting TSPO for TBI treatment and the mechanisms underlying the neuroprotective effects of TSPO drug ligands in neurotrauma.